Bluff - lying - in poker is a case of what Onora O'Neill terms selective falsehood. Let her explain this idea before I go further :
Another alluring, but on reflection impossible, maxim of communication to which Kant turned his attention (in a form few of his admirers find adequate) is that of falsehood. ... [I]t appears that a maxim of falsehood in communication could not serve as a universal principle of communications among a plurality of rational beings, or beings who are becoming rational. For if falsehood became the maxim of "communications" among such beings, comprehension itself would cease, and so also the possibility of communication. This is not to say that a maxim of selective falsehood would be an impossible one for regulating the communicating of a plurality of partially free and rational beings. Plenty of actual communities get on well with a universally shared convention of falsehood in response to intimate inquiries or about punctuality or in relations with strangers. But the very possibility of recognizing what is said in such contexts as falsehood presupposes comprehensibility, and thus also that standards of truth-telling obtain more generally in such communities.' (O. O'Neill, Constructions of Reason : Explorations of Kant's Practical Philosophy, Cambridge : CUP, 1989, 45.)
The main point is that what is up for universalisation in your question is not lying simpliciter but a mutually voluntary activity (the game of poker) in which people agree for purposes of gain or entertainment to engage in a competition with specific other persons in which they and the others know that lying (within limits) is allowed. This is selective lying.
There is no reason why the maxim, 'agree for purposes of gain or entertainment to engage in a competition with specific other persons in which they and the others know that lying (within limits) is allowed', cannot be universalised - that it involves a contradiction in conception or a contradiction in the will.
But the reply may come : Kant rules out lying and you cannot get around this by contextualising lying. Why not ? Two points : first in the Groundwork the prohibition on lying precisely is contextualised : it is contextualised to making a lying promise to repay a debt (§§ 18-19). While the maxim behind this cannot be universalised, the maxim behind my poker case can be.
And in 'On a Supposed Right to Lie from Philanthropy' Kant says :
Truthfulness in statements that one cannot
avoid is a human being's duty to everyone, however great the disadvantage to him or to another that may result from it ... (SRL 8:426). (McGregor Cambridge tr.)
The immediate context is the supposed right to lie to the murderer at the door. But lying in poker is hardly a violation of 'Truthfulness in statements that one cannot avoid'. It is, and is recognized as, selective lying.
The second point is that we need to draw a distinction between what Kant thought the universalisation constraint implies in particular cases or types of case, and what it actually does imply. Even if Kant had pronounced against bluff in poker, it would not follow that the universalisation constraint cannot, as I have argued above, consistently allow it.